#pragma once
#include<iostream>
#include<stack>
using namespace std;
#define valueType int
namespace GIS20205
{
	struct node
	{
		valueType value=0;
		node* left = nullptr;
		node* right=nullptr;
	};

	stack<node> sta;
	void postfirst(node* root)
	{
		if (root==nullptr)
		{
			sta
		}
	}
}